Redshank – the ‘warden of the marshes’

blog nesting RKAre subsidies that are designed to protect the biodiversity of Britain’s saltmarshes, delivering the planned, conservation benefits? In particular, is this investment supporting populations of amber-listed Redshank?

About 25,000 pairs of Redshank are thought to breed in the United Kingdom (link to APEP), with about half of these nesting in coastal saltmarshes. In recognition of the importance of saltmarshes, agricultural grants are available to support their management, with a focus on providing an appropriate level of grazing for a range of plants, birds and insects. In their 2019 paper in the Journal of Applied Ecology, Lucy Mason and her RSPB colleagues ask some serious questions – are these agricultural subsidies being well spent?

Saltmarsh grazing is an important conservation prescription that is used to try to boost, or at least maintain, populations of breeding waders, particularly Redshank, as well as to conserve the unique herb-rich habitats in which they hide their nests and raise their young. This study follows on from an earlier paper that showed that more than 50% of saltmarsh-nesting Redshank in Great Britain were lost between 1985 and 2011, and three papers by Elwyn Sharps on the impacts of cattle that graze saltmarshes during the Redshank breeding season (about which there is more below).

Why worry about Redshank?

The latest population estimate for Redshank in the United Kingdom is 25,000 pairs, as many as 50% of which are birds nesting on saltings. Redshank is an amber-listed species of conservation concern in the UK, with the most recent population changes showing a drop of 44% between 1995 and 2017 (Breeding Bird Survey) and a larger decline over the period since 1990.

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What are saltmarshes?

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Rich plant communities

Saltmarshes are intricate, dynamic habitats, where land meets sea. They are highly productive ecosystems, rich in plants, birds and insects. Traditionally, they would have been grazed by herbivorous mammals and waterfowl but, in the absence of free-roaming animals, the only way to maintain the short but diverse swards favoured by specialist plants and animals is to employ the services of cattle and sheep. Although saltmarsh still covers large areas, it is estimated that over 50% has been lost or degraded globally, thanks to reclamation and erosion. Further losses are occurring, as saltmarshes get squeezed between rising sea levels and the hard sea defences that protect coastal settlements and farmland.

The structure of saltmarsh is created by the way that water moves, as waves dissipate their energy and deposit silt during higher, spring and storm tides and the water then runs back off the salting. The latter process creates branching creeks that drain the marsh, from small meandering ditches, that are just big enough to catch a foot and twist an ankle, to waist-deep, fast-flowing channels with slippery, muddy sides.

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Deep creeks of outer marsh

Anyone who has been out on a marsh will know that, with some local knowledge, it is possible to make your way from the sea-wall to the edge of the saltmarsh along a route that lies between two creek systems. On the other hand, travelling along the muddy, salting edge parallel to the sea-wall is difficult, as it involves crossing creeks. Grazing animals face the same navigation problems; it’s a lot easier to graze wide expanses of the upper marsh than the outer areas that are dissected by deep creeks. As discussed below, these upper areas, with a mixture of short grass and clumps of longer grass, are also the ones that are favoured by breeding Redshank.

How many Redshank breed on saltmarshes?

A 2013 paper by Lucy Malpas (now Lucy Mason) in Bird Study brought together evidence of declines in saltmarsh-breeding Redshank over a 26-year period. An estimated total of 21,431 pairs were found to be breeding on British saltmarsh in 1985 but this had dropped to 11,946 pairs in 2011, with the highest proportion of the remaining population found in East Anglia. The 2011 survey showed that there were regional variations (see table), with the biggest declines in Scotland. Looking at the way that saltmarshes were managed, Lucy found that Redshank declines were less severe on conservation-managed sites in East Anglia and the South of England, where grazing pressures remained low, but more severe on conservation-managed sites in the North West, where heavy grazing persisted.

tableAt the end of this Bird Study paper, Lucy and her colleagues suggest that saltmarsh-breeding Redshank declines are likely to be driven by a lack of suitable nesting habitat. Conservation management schemes and site protection, implemented since 1996, appeared not to be delivering the grazing regimes and associated habitat conditions required by this species, particularly in the northwest of England. Although habitat changes may not be linked to unsuitable grazing management in all regions, they suggested the need for a better understanding of grazing practices and consideration of potential long-term management solutions.

Grazing levels and Redshank numbers

Intensive grazing leads to a very short uniform sward, lighter grazing produces a more uneven patchy sward with diverse heights, whilst no grazing can leave saltmarshes with dense communities of coarse grasses. For Redshank, that need clumps of grass in which to hide their nests and more open areas in which chicks can feed, light grazing is a key management tool.  Elwyn Sharps and colleagues, working on the salt marshes of the Ribble Estuary in northwest England, were interested to see how grazing regimes worked for the local Redshanks. Elwyn showed that the risk of Redshank nest predation increased from 28% with no breeding-season grazing to 95% with grazing of 0.5 cattle per hectare per year, which is still within the definition of light grazing.

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In follow-up work, Elwyn showed that livestock play an important role in creating the clumps of Festuca rubra habitat preferred by Redshank nesting on the Ribble Estuary but that even low-intensity conservation grazing can create a shorter than ideal sward height, potentially leaving Redshank nests more vulnerable to predators. There is more about this in the WaderTales blog: Big Foot and the Redshank Nest.

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Grazing the higher saltmarsh

One of the missing elements from Elwyn’s first two papers about grazing levels was an understanding of the behaviour of cattle on saltmarsh. In the next piece of work, Elwyn and colleagues tracked the movements of individual cattle, using GPS collars, and assessed the vulnerability of nesting Redshank, using dummy nests. In a 2017 paper in Ecology & Evolution, they showed that cattle spend their time in the same areas of saltmarsh as the ones in which Redshanks like to nest. Their conclusion is that “grazing management should aim to keep livestock away from Redshank nesting habitat between mid-April and mid-July, when nests are active, through delaying the onset of grazing or introducing a rotational grazing system”.

Do conservation payments deliver?

To assess whether conservation grazing is being achieved, and whether agri-environment schemes are effective in delivering this management, Lucy Mason and her colleagues conducted a national survey of English saltmarshes, scoring the management on each site as optimal, suboptimal or detrimental, based on five aspects of grazing (presence, stock type, intensity, timing and habitat impact). They surveyed 213 saltmarsh sites in three regions during 2013, representing 50% of the vegetated saltmarsh in England. Of the study sites, 114 (54%) received payments for saltmarsh management and/or conservation grazing options through Higher Level Stewardship, or the Countryside Stewardship Scheme. The annual cost of saltmarsh and grazing management options in the marshes that were studied was £543,075 for 10,218 ha of saltmarsh, equating to over £5 million spent on saltmarsh management options over the course of 10 years.

blog muddy creekTo assess grazing levels, the team visited each site up to four times during the core grazing period (April–October), to count cattle. They also assessed the longer-term impact of grazing on saltmarsh habitat, by measuring sward height and heterogeneity. Combining the measurements of site condition and analysing the results produced the following key findings:

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    Nest hidden in clump of grass

    Although most saltmarsh sites in England that are capable of supporting grazing are grazed by livestock, conservation grazing is not being achieved.

  • Nationally, the biggest management failings relate to the timing of grazing and the way that grazing impacts upon habitat structure.
  • There were regional differences in scores relating to stock type, grazing intensity, grazing timing and habitat impacts, but no single region scored higher than others overall.
  • Sites with Agri-Environment Scheme (AES) agreements were no more likely to be grazed than sites without AES – some subsidies were being paid without any active grazing taking place.
  • AES reduced grazing pressure but not sufficiently to achieve optimal conservation grazing requirements, indicating that AES has been an ineffective conservation mechanism on saltmarsh.
  • In the East, older AES sites scored substantially higher and approached optimal levels, suggesting that managers and advisers can improve outcomes by working together over longer periods.

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Improving the system

The authors argue that, although there is sound scientific evidence as to how saltmarshes should be managed, to provide positive conservation outcomes, there are problems when it comes to the translation of evidence into recommendations for hands-on management. It is also difficult to encourage land managers to implement recommendations when these go against traditional farming practices and economic gain. To improve the situation, Lucy and her colleagues suggest that:

  • When establishing agreements, it is helpful to provide detailed prescriptions that can guide land-managers.
  • AES payments need to take account of the costs of grazing a complex environment, which means thinking about the availability of cattle of appropriate ages at the right times of year, provision of fresh water and high-tide refuges, and the use of fences to divide up the saltmarsh, in order to provide a rotational grazing system.
  • Prescriptions that focus on numbers of cattle and timing of grazing are easier to follow than ones that focus on intensity and habitat condition.
  • Additionally, a more detailed and reliable system of auditing would be beneficial, to ensure that management activities take place to the necessary standard prior to payments.
  • Moving to a results-based scheme, where payments are made based on desirable outcomes, rather than on evidence of management, may improve the overall conservation value and economic efficiency of saltmarsh AES options.

Blog JoshIn conclusion

Raising cattle on saltmarsh is hard work, in terms of stock control, but requires no fertiliser inputs.  These ‘mobile mowing units’ stop saltings from becoming long and rank, thereby creating spaces in which a rich plant and grass community can flourish, where geese and waterfowl can graze during the winter months, and potentially providing nesting spaces for breeding waders, such as the amber-listed Redshank, breeding numbers of which are still declining.

Lucy and her RSPB colleagues conclude that Agri-environment Schemes are the only mechanisms through which saltmarsh conservation grazing can be implemented on a national scale, so it’s important to make sure that they are as effective as possible. By working together, it is hoped that policymakers, researchers and managers can refine conservation guidelines which are used to create management schemes that attract subsidies. They suggest that better value could be achieved through more sensitive use of current management activities or perhaps by linking payments to conservation outcomes, rather than on evidence of management.

blog cr RKThe noisy warning calls of a pair Redshank, as they encourage their chicks to hide, have earned the species the title ‘warden of the marshes’. Their calls also appear to be a warning cry about the state of Britain’s saltmarshes, despite the large amount of money being provided through agricultural subsidies and the good intentions of conservation organisations, agricultural advisers and graziers.

You can read more here:

Are agri-environment schemes successful in delivering conservation grazing management on saltmarsh? Lucy R. Mason, Alastair Feather, Nick Godden, Chris C. Vreugdenhil & Jennifer Smart. Journal of  Applied Ecology. May 2019.

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GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton

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Not-so-Common Sandpipers

April and May mark the start of the Common Sandpiper breeding season, as males display along rivers and streams and around the banks of lakes and reservoirs. Numbers in the United Kingdom have declined by 26% in just over 20 years, providing an increased focus to research that has been taking place over five decades.

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This tale focuses on a year in the life of Common Sandpipers, using material gleaned from the book Common & Spotted Sandpipers by Phil Holland (published by Whittles in 2018) but with new information from recent migration studies. Phil’s fascinating book also includes chapters about the habitats used by both species, the food that they eat, predators that eat them and the way that Common Sandpipers have adapted (or failed to adapt) to changes in Britain over the last 250 years.

Common or Spotted?

blog spottyThis blog is just about Common Sandpipers. The Spotted Sandpiper breaks up the circumpolar distribution of the Common Sandpiper, laying claim to the Americas. A big difference between the two species is the mating system, with Common Sandpiper pairs setting up territories in a conventional (although not particularly faithful) manner and Spotted Sandpipers using polyandry in a way that provides females with the potential to raise more chicks in a year.

A female Spotted Sandpiper sets up a territory, attracts a male, lays a clutch of eggs which her partner then incubates, attracts and lays another clutch for another male, and so on. In Phil Holland’s book, there is an example of one female laying five clutches with three males over the course of six weeks – representing an egg-mass of four times her own body weight. There is plenty more fascinating stuff about Spotted Sandpipers in the book.

Population changes

The Breeding Bird Survey indicates a fall in breeding Common Sandpiper numbers in the UK of 26% between 1995 and 2017, with a bigger decline in England (49%) than in Scotland (23%). Other BTO-led surveys suggest that the nationwide declines started in the mid-1980s, with a British fall of over 50% during this longer period. There have been similar declines elsewhere in Europe. Common Sandpiper is now amber-listed, as a species of conservation concern, in the UK.

Breeding season

Much of the detailed breeding season work on Common Sandpiper in the UK was undertaken in the English Peak District by Phil Holland and then Derek Yalden, to whom Phil Holland’s book is dedicated, with information supplemented by other bird ringers, particularly Tom Dougall in Scotland.

blog nestMale Common Sandpipers tend to arrive back from Africa a little earlier than females – with a median difference of just two days – and it is the male that holds the territory (females in Spotted Sandpiper). If two birds that were together in the previous year arrive back on site then they will usually pair up again. When they don’t, it’s because of a mismatch in the timing of arrival or because the female moves to a better territory or more experienced mate. It may not be easy to spot infidelity in the field but genetic analysis in Scotland showed that males were incubating the eggs that had not been fertilized by them in 5 out of 26 cases (Mee paper link). On two of these occasions, none of the clutch of four belonged to the male that was sitting on them.

blog sittingDuring the incubation period, males typically take the 15-hour night-shift and females the 9-hour day-shift. During their ‘time off’, males devote time to territory defence and look-out duties. Chicks hatch after three weeks and the growth rate of chicks is highest in warm, dry and sunny weather. Males do most of the parenting of chicks; females usually leave before the chicks fledge and occasionally, if there are late nests, before the eggs hatch. Experienced parents raise more chicks to the point of fledging. There is more fascinating detail in the book, which includes full references for papers.

The southward migration

blog mapMovements of ringed birds from Scotland and Northern England strongly suggested that adults left their breeding territories and headed south within the UK, to fatten up prior to migration to Africa. British ringers have caught birds weighing up to 80 g, twice the pre-fattening weight, suggesting the potential to move a long way in the next flight.

Geolocators have been a revelation, enabling individuals to be tracked for the whole annual cycle between one breeding season and the next. The story of the first UK Common Sandpiper to return with a functioning geolocator was told in Wader Study by Brian Bates and colleagues, revealing two stops in western Britain, a three-day break in Morocco and a direct flight to Senegal.

There’s a WaderTales blog about the use of geolocators on Green Sandpipers that gives more information about how data are collected and discusses how these devices affect the behaviour of the birds that carry them.

A follow-up paper by the same Scottish team from Highland Ringing Group, this time with Ron Summers as lead author, has been published in the Journal of Avian Biology (Non-breeding areas and timing of migration in relation to weather of Scottish-breeding common sandpipers). It summarises the journeys of 10 tagged birds, with a median departure date from Scotland of 9 July. Some individuals spent time fattening in England, then most birds staged for longer in Iberia before continuing to West Africa, with a median arrival time of 28 July. The southward migration from Scotland took an average 17.5 days (range 1.5–24 days), excluding the initial fuelling period.

Pere Josa and colleagues have studied Common Sandpipers in The Ebro Delta of Spain, writing up their findings in Wader Study as Autumn migration of the Common Sandpiper. These stop-over adults migrate seven weeks earlier than juveniles, putting on enough fat to travel at least 2000 km on the next stage of their journeys, which would take them to North Africa. They would need to refuel if they were to make it as far as West Africa, which is the main wintering area for Common Sandpipers. Common & Spotted Sandpipers provides many more examples of ringing and body condition studies carried out in stop-over sites between Sweden and Morocco.

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Life in the south

blog mangroveSix of the tagged birds from Scotland spent most of the non-breeding season (October–February) on the coast of Guinea-Bissau, suggesting that this is a key area. Single birds occurred in Sierra Leone, Guinea, the Canary Islands and Western Sahara.

Coastal West Africa provides two major habitats for Common Sandpipers: mudflats associated with mangroves (as shown to the right) and rice fields. Phil Holland takes the reader around the mangroves of the world and discusses the numbers of Common and Spotted Sandpipers that have been reported from different countries. He suggests that rice fields provide supplementary food for birds that are mainly coastal winterers and wonders if the depletion of mangrove habitat  has affected Common Sandpipers.

The northward migration

The last day in West Africa, for the 10 tagged individuals, ranged from 3 to 20 April and the arrival dates in Scotland ranged from 19 April to 6 May. The birds typically staged twice between Morocco and the Channel and the median time taken for active migration was 16 days (range 13.5–20.5 days). The main migration strategy involved short- and medium-range flights, using tail-winds in most cases. Birds that left later spent shorter periods of time at stop-over locations.

Why so few Common Sandpipers?

survival blogAs discussed in the WaderTales blog summarising Patterns and processes in shorebird survival rates: a global review by Verónica Méndez in IBIS, the apparent annual survival rate of the Actitis family is low, with a calculated rate of 0.718 for Common Sandpiper and 0.497 for Spotted Sandpiper. Whether this has always been the case is unknown, of course, and Phil Holland points out that these calculations are based upon observations of colour-ringed individuals, at least some of which change territories between years, potentially leading to a reduction in detectability.

An analysis of demographic data for a small population of Common Sandpipers in northern England, by James Pearce-Higgins and colleagues indicated that the long-term decline in numbers was not due to low breeding success, instead being due to a low return rate of adults, which was negatively associated with the winter North Atlantic Oscillation. This suggested that climate change might be affecting annual survival.

In their paper about the 10 Scottish birds, tracked using geolocators, Ron Summers and colleagues matched movements to meteorological data during the migration period. They suggest that the weather during the southward migration was unlikely to adversely affect birds but that strong cross-winds or head-winds during the northward migration to the breeding grounds may do so. This accords with work on Black-tailed Godwits by Nathan Senner and colleagues which showed that the survival of satellite-tagged birds was reduced on the northward crossing from West Africa to Europe.

For the moment, there is no clear explanation for the fall in Common Sandpiper numbers. Given that it’s hard to change the climate or to study what might be happening to Common Sandpipers feeding amongst the mangroves of West Africa, it seems wise to focus on habitat and species protection in breeding areas. We also need to keep monitoring productivity and return rates of breeding populations in the UK and elsewhere, especially in the English Peak District.

Common & Spotted Sandpipers

blog coverPhil Holland’s book is a fascinating insight into the lives of the two Actitis species. It’s almost as if the reader is allowed to sit on a bank with the author and share intimate moments with these birds. Derek Yalden would have been delighted to see the project come to fruition but acknowledge that there is still much to learn. Who will spend the next 40 years studying Common Sandpipers in Europe and Africa or Asia and Australasia, or Spotted Sandpiper in the Americas?

Book Details

Common & Spotted Sandpipers is published by Whittles Books. You can find out more by following this link.

New research

blog CKThomas Mondain-Monval (Lancaster University) is trying to understand the UK-decline of Common Sandpipers.  He is studying a breeding population in the Yorkshire Dales National Park, tracking birds on migration and studying them at a wintering site in Djoudj National Bird Sanctuary, Senegal.  Birds are fitted with colour rings and geolocators in the UK and Senegal, and Thomas would appreciate reports of migrating birds, which are likely to appear in Iberia, France and England. If licensed bird-ringers see birds with geolocators and spot opportunities to catch them and remove the trackers, this would be very helpful. Thomas can be contacted at:

t.mondain-monval@lancaster.ac.uk


GFA in Iceland

WaderTales blogs are written by Graham Appleton, to celebrate waders and wader research.  Many of the articles are based on previously published papers, with the aim of making wader science available to a broader audience.

@grahamfappleton